But an attorney for the whistle-blower officer, Detective Joseph Crystal, believes the efforts are "way too little, way too late" and said the investigation has taken so long that any officers implicated could not be disciplined because the statute of limitations has run out.

In a rare move, the investigators working the case were pulled from outside of the city, according to Crystal's attorney, Nick Panteleakis. Two are lieutenants with the Philadelphia Police Department, and two work for the Montgomery County Police Department.

He said their work began about a month ago, and they have interviewed Crystal and other officers. The Baltimore Police Department did not respond to a request for comment for this article.

The investigation grew out of an October 2011 drug arrest. Officers saw a man throw away suspected drugs and tried to chase him, then later found him hiding in the home of a police officer's girlfriend.

After he was handcuffed and put in a wagon to be taken away, police brought the man back into the house and Officer Anthony Williams, who was off duty, beat him. Williams was convicted of assault and obstruction of justice, and Sgt. Marinos Gialamas was found guilty of misconduct.

Word of the potential misconduct by police only reached the state's attorney's office through back channels, according to arguments ahead of the officers' trial, after Crystal contacted a prosecutor he knew.

A few weeks later, in November 2012, a rat was found on Crystal's vehicle, which he believed was from officers sending him a message that he was viewed as a snitch.

Prosecutors said they could not find sufficient evidence to prosecute anyone.

After the incident became public in February 2014, Batts said Crystal had his full support and would be looked after. He told the council that he is in regular communication with Crystal.

Panteleakis confirmed that Batts has been in regular contact with Crystal, but he said the officer continues to be mistreated by the department. He said Crystal has had his assignment within the department changed four times in the past three weeks, including three times in a 10-day stretch.

"I don't see that as backing someone up," Panteleakis said.

He also said that some of Crystal's allies who have been interviewed by the investigators were labeled "suspects" and the agency opened internal complaints against them, which upset the officers and Crystal.

"We said, 'That's not correct, we don't want open [internal affairs] complaints against them,' but they said, 'We're going to keep them open,' " Panteleakis said.